Artists' canvases ordinarily are stretched on frames comprised of four straight wooden boards ("stretcher boards") secured together in a rectangle, over the top of which the canvas is pulled taut and fastened along the edges. Occasionally, the internal outline of one or more stretcher boards becomes visible when the painting is hung. These "ghost" shadows are unsightly and detract from the viewer's appreciation of the artwork.
Typically, this occurs in one of two ways. Either the canvas sags back against the frame when hung for display and shadows temporarily reveal the internal outline of the stretcher, or, as the artist creates the painting, he or she pushes too hard on the brush, leaving permanent marks as the brush drags over the inner edge of the wood (in the manner that charcoal rubbings are made of works formed in bas-relief).
The common method of preventing these effects is to raise the outer edge of each stretcher slightly in order to lift the canvas off the horizontal plane of the board, except for a narrow portion at this very outer edge. This raised edge may be routed into the board, or (referring to the prior art frame shown in FIG. 3) a firring strip 240 may be affixed by nails 241 or glue onto the upper surface of the stretcher board 242. However, this method is impractical for canvases shaped in non-rectilinear forms, such as circles, ovals and like curvilinear outlines. These canvases usually are mounted on sheets of plywood which previously have been cut into the desired shape. Precisely-curved firring strips are unavailable (insofar as wood does not readily bend), and plywood mounting panels are not easily routed. On the other hand, while one would be able to paint with the canvas mounted directly on the top surface of the mounting panel without leaving such trace marks, painters usually prefer the spring of stretched free canvas.
Prior developments in this field may be generally illustrated by reference to the following information disclosure statement:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 3,830,278 L. Packer Aug.20,1974 5,133,140 J. Frey Jul. 28, 1992 2,456,225 C. Thomas Dec. 14, 1948 4,947,561 T. Delacroix et al. Aug. 14, 1990 5,115,584 R. Lucchetti May 26, 1992 4,991,329 W. Wilson Feb.12, 1991 4,279,087 A. Crawford Jul. 21, 1981 4,179,830 T. Lamb Dec. 25, 1979 ______________________________________
U.S. Pat. No. 3,830,278 teaches an extruded edging 11 for a canvas, the edging having an L-shaped cross section. Separate corner pieces are attached to the edging after it has been stretched across the frame, to secure the canvas in a rectilinear configuration.
U.S. Pat. No. 5,133,140 teaches a channel molding for a canvas frame that fits around the edges thereof and has pointed barbs with which to secure the canvas.
U.S. Pat. No. 2,456,225 teaches L-shaped angle irons 4 for a canvas frame which grip the canvas with pointed tongues.
U.S. Pat. Nos. 4,947,561 and 5,115,584 teach extruded frame edgings having complex, longitudinally rigid, cross sections for use in making frames comprising rectangles and like rectilinear polygons. The rest of the patents are representative of what was found in the art.
The prior art devices are designed not to bend lengthwise laterally (from side-to-side) to follow the shape of edge of the frame, which is assumed in said devices to be straight, except for angled corners.
Therefore, for use with canvases having curved edges, there is a need for an edging device that is designed to bend easily laterally along its longitudinal axis during its application to the backing board or frame, yet, on the other hand, that is designed to resist lateral deformation from top to bottom when pulled inwardly by stretched canvas.
To avoid confusion between the two types of lateral stability (horizontal and vertical), hereinafter, the tendency of a device to resist or allow lateral deformation along its longitudinal axis will be called "longitudinal" stability or flexibility, respectively, and the tendency of a device to resist or allow lateral deformation within vertical planes passing perpendicularly through its longitudinal axis will be called "upright" stability or flexibility.